Question

Sorry for the silly question. I just started C# programming. I’ve been researching this for many hours now, and read what I could here. This is seemingly so common, I just do not understand why it does not work. I want to declare a variable in a parent method and change the value in a child class. If this isn’t the way to do it, how can I make methods (even for loops or while loops) that return useful data?

Example 1:

   static void Main(string[] args)
    {
        int rowID;
        for (int i = 1; i < 500; i++ )
        {
            rowID = i;
        }
        Console.WriteLine(rowID);
    }

Example 2:

private void SendButtonClicked(object sender, System.EventArgs e)
{            
    // finds the first row that has not been sent
    int rowID = GetMessageRow();
    //then process the row and figure out what stored procedure to run 
    RunStoredProcedure(rowID);
}

public int GetMessageRow()
// finds the first row that has not been sent
{
    int rowID;
      // skipping some code
       while (drGetMessageRow.Read())
        {
         // while loop does not understand the variable and errors  
            rowID = drGetMessageRow.GetInt32(0);
            MessageBox.Show("1: RowID is " + rowID.ToString());
        }
}

Answer 1

Your GetMessageRow method needs to return rowID. This is what allows rowID (which is a different variable) to have its value set in the SendButtonClicked method.

public int GetMessageRow()
// finds the first row that has not been sent
{
    int rowID;
    // skipping some code
    while (drGetMessageRow.Read())
    {
        // while loop does not understand the variable and errors  
        rowID = drGetMessageRow.GetInt32(0);
        MessageBox.Show("1: RowID is " + rowID.ToString());
    }

    return rowID;
}